Question

ondisconnect（）不起作用。即使断开与Internet的连接后，firebase数据库中的用户状态仍保持为true。我希望将其更改为ServerValue.TIMESTAMP ....................... ................................................... ................................................... ........

>     java

    package com.example.connect;

    import android.app.Application;

    import androidx.annotation.NonNull;

    import com.google.firebase.auth.FirebaseAuth;
    import com.google.firebase.database.DataSnapshot;
    import com.google.firebase.database.DatabaseError;
    import com.google.firebase.database.DatabaseReference;
    import com.google.firebase.database.FirebaseDatabase;
    import com.google.firebase.database.ServerValue;
    import com.google.firebase.database.ValueEventListener;
    import com.squareup.picasso.OkHttp3Downloader;
    import com.squareup.picasso.Picasso;

    public class Connect extends Application
    {
        private FirebaseAuth auth;
        private DatabaseReference userDatabase;

        @Override
        public void onCreate() {
            super.onCreate();

            FirebaseDatabase.getInstance().setPersistenceEnabled(true);

            Picasso.Builder builder = new Picasso.Builder(this);
            builder.downloader(new OkHttp3Downloader(this, Integer.MAX_VALUE));
            Picasso built = builder.build();
            built.setIndicatorsEnabled(true);
            built.setLoggingEnabled(true);
            Picasso.setSingletonInstance(built);

            if(auth!=null) {
                auth = FirebaseAuth.getInstance();

                userDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(auth.getCurrentUser().getUid());
                userDatabase.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        if (dataSnapshot != null) {
                            userDatabase.child("online").onDisconnect().setValue(ServerValue.TIMESTAMP);
                        }
                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });
            }


        }
    }

Answer 1

您可以使用对Firebase的自定义引用，它会告诉您用户是否已连接：

DatabaseReference connectedRef = FirebaseDatabase.getInstance().getReference(".info/connected");
connectedRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot snapshot) {
        boolean connected = snapshot.getValue(Boolean.class);
        if (connected) {
            System.out.println("connected");
        } else {
            System.out.println("not connected");
        }
    }

    @Override
    public void onCancelled(DatabaseError error) {
        System.err.println("Listener was cancelled");
    }
});

https://firebase.google.com/docs/database/android/offline-capabilities#section-connection-state

请记住，如果您没有Internet访问权限，这并不意味着该用户已与服务器断开连接，则服务器保留的会话将持续很长时间，直到它打算断开该用户的连接为止。

此代码将知道用户何时断开与数据库的连接。

ondisconnect（）无法正常工作。即使从互联网断开连接后，firebase数据库中的用户状态仍保持为真

1 个答案: